Activation of this pathway is frequently observed in CRC, and might account for overexpression or dysregulation of receptor tyrosine kinases (e.g., EGFR, MET), activation of the nonreceptor tyrosine kinase Src, activating mutations in RAS or in PIK3CA, or downregulation of the tumor suppressor PTEN [4,17,273]. The gene discussed is PIK3CA; the disease is colorectal carcinoma.